(a) Field of the Invention
The present invention relates to an active dynamic vibration absorber, and more particularly, to an active dynamic vibration absorber capable of effectively generating vibration by switching a direction of current applied to a coil part with a simple configuration.
(b) Description of the Related Art
In general, a dynamic vibration absorber is a device for decreasing vibration by generating an anti-node for generated vibration, and is widely used as a device for attenuating vibration in a vehicle.
An active dynamic vibration absorber includes a spring, a mass body, and a driving device capable of making the mass body reciprocate. In particular, in an active dynamic vibration absorber including an electromotive driving device among the active dynamic vibration absorbers, a mass body is fixed to a case by using a spring, and the mass body including a yoke and a permanent magnet and a separate coil part are disposed, so that the mass body reciprocates by Lorentz force generated by applying current to a coil. Through this, inertia force (control force) of the mass body is generated, and the inertia force (control force) is transferred to the case fixed to the vibration body (a chassis of a vehicle body, and the like) through the spring. As a result, vibration force transferred from the vibration body through an insulation system is attenuated, so that the vibration is decreased.
A vibration decrease principle of the active dynamic vibration absorber to which the aforementioned electromotive driving device is applied will be described. As illustrated in FIG. 1 (RELATED ART), an active dynamic vibration absorber 101 is operated so that a mass body 103 reciprocates, and inertia force (control force) is generated by the reciprocating mass body 103.
The number of vibrations (frequency) is variable according to an applied current or voltage, and when the inertia force has a phase opposite to the vibration desired to be decreased, the vibration is decreased by attenuating the target vibration desired to be decreased, that is, vibration force transferred to a vibration body 105.
The number of excitation vibrations (excitation frequency) desired to be decreased may be changed by controlling an operation current applied to the active dynamic vibration absorber 101 or a frequency of a voltage, and a size of inertia force (control force) may also be changed by controlling the operation current or a size of the voltage.
A general active dynamic vibration absorbing system includes an accelerometer for sensing a size, a frequency, and a phase of a vibration of a chassis and outputting a corresponding signal, and a controller for controlling the active dynamic vibration absorber 101 by receiving the corresponding signal of the accelerometer and an engine rotation speed signal.
In the active dynamic vibration absorber 101 having the aforementioned configuration, when current is applied to a coil through a drive device and then stops, back electromotive force (counter electromotive force) is generated while energy left in the coil flows in a reverse direction. In this case, when a large back electromotive force is generated, the drive device may be damaged. In order to prevent this problem, it is possible to use a method of protecting the drive device by installing a diode between a coil part and a power part in a reverse direction, and making the back electromotive force be absorbed at a side of the power unit.
However, the aforementioned active dynamic vibration absorber 101 of the related art needs to selectively control only a target frequency desired to be attenuated, so that it is necessary for a control signal to have a sinusoidal waveform. Accordingly, there is a problem in that a design of an output unit of the controller becomes complex, and a manufacturing cost is increased because free wheeling needs to be implemented by using a diode and the like in order to protect a device and improve efficiency, and an H-Bridge circuit needs to be applied in order to generate a control signal in a forward direction (+) and a reverse direction (−).
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.